Charles e



Nov. 20, 1928.,

C. F. ESTWICK AUTOMATIC TRAIN CONTROL SYSTEM Original Filed March 7, 917

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NVE/VTOR WMYQMW A TTORN E Y Patented Nov. 20, 1928.

UNITED STATES PATENT OFFICE.

CHARLES F. ESTWICK, OF ROCHESTER, NEW' YORK, ASSIGNOR 'IO GENERAL RAILWAY SIGEIAL COMPANY, 013 GATES, NEW YORK, A CORPORATION OF NEW YORK.

AUTOMATIC TRAIN-CONTROL SYSTEM.

Application filed. March 7, 1917, Serial No. 152,972 Renewed December 7, 1926.

This invention relates to automatic train control systems, and more particularly to a means for establishing a communication between a vehicle or train and devices along the track.

One of the important requisites of an automatic train control system is the means for communicating from apparatus or devices along the track to a. train traveling over the track, and it is desirable to construct and arrange this means such that a reliable and ellicientcommunication maybe had continuous- 1y at all points in the travel of the train. It is also desirable that this means of communication should be of the inductive type, that is, the act of communication should be performed through space with-out actual physical contact. Furthermore, it is desirable to use so far as possible for this purpose parts or devices which are already a part of the railway system, such as the track rails.

\Vith these considerations in view, one of the principal objects of this invention is to devise a simple and reliable means for establishing communication between the track rails and a moving vehicle.

I A further object of the invention is to devise a means of communication between the track rails and a moving vehicle which is applicable to electrically propelled roads.

Other objects and advantages will appear more fully hereinafter as the description of the invention progresses, and the novel rea tures of invention will be pointed out in the claims.

In describing the invention in detail, reference is made to the accompanying drawings in which are illustrated preferred embodiments of the invention, and in which like refcrencc characters refer to like parts in the several views.

Fig. 1 is a diagrammatic view inthe nature of a wiring diagram illustrating the electrical circuits and simplified forms of devices embodying this invention applied to an electrically propelled railway: Fig. 2 is a fragmentary view illustrating the application of the system embodying this invention to an ordinary railway: and Fig. 3 is a fragmentary view illustrating a modification.

Referring to the accompanying drawings the numerals 1 and 2 designate the usual track rails of the railway track which, according to the particular embodiment of the invention illustrated, are divided by insulated joints 8 into track sections or blocks of the desired length. In Fig. 1 the invention is shown applied to an electrically propelled road of the type in which the propulsion current is supplied to the trains by means of a. third rail R, the source of propulsion current, shown as a generator G, being connected across the third rail and one of the track rails2. Each motor car or locomotive is provided with a suitable form of contact shoe S adapted to make electrical contact with the third rail R, and this contact shoe S is connected through suitable controlling devices D to an electric motor M used for propelling the cars, all in accordance with the well known and established practice. In order to permit the propulsion current to flow along the track rails 1 and 2 to the power stat-ion, and at the same time prevent the flow of the alternating current used for signaling purposes from one track section or block to another, impedance bonds I are used; and since the construction, operation and general features of these impedance bondstis well known to those skilled in the art, further explanation is unnecessary. Extending along the railway track is a transmission line 4 which is supplied with alternating current of a certain frequency from a suitable enerator 5. In practicing this invention it ecomes necessary to have a source of. alternating current of diiierent frequency than that supplied by the transmission line 4; at one end of each block, and while this alternating current of diiierent frequency may be obtained in various ways, according to the embodiment of the invention illustrated, ascparate transmission line 6, supplied with ltcrnating current from a suitable generator 7 capable of supplying current at a difierent frequency than the generator 5, is shown extending along the-track.

The electrical connections and parts associated with the several blocks are the same and for convenience corresponding parts and electrical connections are given the same reference characters with distinctive exponents added. At one end of each block, preferably at the exit end, is located a track transformer T, the primary of which is connected across the line wires of the transmission line 4 and the secondary of which is connected by means of conductors 8, 9 and 10, 11 across the track rails 1 and 2 of the corresponding block. At the otherend of each block is a track relay 12 which is connected across the former T. Each of the track relays 12 is- PIOVlQlGtl with an armature or contact finger 13 shown conventionally in the drawing. Located at the exit end of each block is a signal transformer N the primary of which is con nected across the line wires of the transmission line 6 and the secondary of which is connectcd inacircuit including the armature 13 of the track relay 12 of the next block in advance and terminating at the track" rails 1 and 2, said partial circuit consisting of con doctors 9, 14-, 15, 16 and 11.

' Carried by each vehicle traveling over the track is a coil K which is located in front of the foremost pair of wheels and axles'of the vehicle or train and'which is arranged in inductive relation to one of the track rails, as the trackrail 2. Only one such coil K is shown in the drawing, but it will be apparcut as the description of the invention progrosses, that another like coil K arranged in inductive relation with the other track rail l may be used if desired. The current induced in the coil K is very feeble and in order to use this current for practical purposes, such as operating a relay, it becomes necessary to amplify or magnify this current by suitable means. In accomplishing this result by the particular type of amplitier shown in the accompanying drawing, an electro nagnetE is-included in a circuit connected to the terminals of the coil K, and the armature '17 of this electro nagnet E bears upon a pile of carbon discs 18 which rest upon a base 19 of electrically conducting mate vrial. It will be apparent to those skilled in the art that the feeble variations in the current flowing through the electromagnet E will cause slight movements of its armature 17 which will vary the pressure upon. the carbon discs 18 so asto cause a variation in the resistance of the carbon pile between the armature and its base plate 19. If the variations in the current flowing through the electromagnet E are alternating in character and of a predetermined frequency, the variation in'the resistance of the carbon pile 18 will also be of a predeterminedfrequency. In order toutilize this periodic variation in the resistance of the carbon pile for the useful purpose of controlling cab signals or automatic train control apparatus, a sensitive relay F, illustrated in a simplified form in the drawi11g,-is connected in a circuit including a suitable source ofcurrent-as a battary 20 which comprises conductors 21, 22 and 23.

- The sensitive relay-F illustrated is of the olarizedreed' t 1 3e and in eneral com arises a permanent magnet 24: having an upper pole piece 2l in which is lined one end of a reed 25. The lower end of tlleperinanentmagnet 2 1 is formed with opposite U shaped pole pieces Secured to the base 27 ofinsulating material are two flexible contact springs 28 disposed on opposite sides of the reed 25; and also secured to said base are adjustable conacts 29 with which the contact springs 28 may make electrical contact. The flow of periodic fluctuating current through the coils 26 of the sensitive relay tends to vibrate the reed 25, and if the frequency of this fluctuating cru'rent corresponds to the natural period of vibration of said reed, the amplitude of the vibration of said reed is great enough to causet'ie'contact springs 28 to make electrical contact with their respective contacts 29. 'llhc natural period ofvibration of the contact springs is preferably so selected that while the reed 25 is vibrating in its natural {)QTlOlLllY-fit} contact springs 28 are, practi- (sally contiruiously in contact with their re-' spective c itacts 29. r

The sensitive relay F may be used for controlling cab signals or any suitable form of auton'iatic train control apparatus. Since the particular construction of the train control apparatus forms no part of the present invention, such apparatus hasbeenindicated generally by the d'evice H which is preferably connected in a normally closed'circuit includingthe circuit controller governed by the sensitiverelay F, the, arrangement being preferably employed so that theautornatic rain control apparatus His in its normal or inactive condition when supplied with current and automatically assumes its control ling condition when deprivedof current, the normally closed circuit including said apparatus H being automatically opened by the deenergization of the sensitive relay F.

Included in the conductors connecting the coil K to the electromagnet E are an adjust,- able reactance X and a condenser C arranged series, the, purpose of this reactance and condenser being explained hereinafter in connection with the description of the opera tion. 1 7

Q Operation: l-lssuming a train or vehicle is traveling in the block A, as shown in Fig. 1, and that no other train occupies the block B in adiiifce.

Under these conditions the track, relay 12 at the block B is energized,

so for rai and 2. This currcntliows along one tracl: rail through I the wheels and axles of the vehicle and back along the other track rail. The current in one of the rails, as the t3 cl; rail 2, induces like currents of the same freauency in the coil 15 and this induced cur- *ent passes through the electroinagnet E; flew oi? altcrnatingcurrent through no elecannagnet E pointed out hereinhefore, causes an amplified periodic current of the same frequency to flow through the sensitive relay F, thereby energizing its coils and closing the circuit controller operated thereby, so as to retain the train control apparatus H in its normal or inactive condition. The sensitive relay F is preferably constructed so as to respond to currents of one frequency only which frequency is the same as that of the transmission line 6. In this way, so long as current of a given frequency is supplied from the transmission line (3 to the track rails, the sensitive relay F on the train remains energized and the train control apparatus H on said train in its normal or active condition.

In case a train should enter a block, as the block A, when the next block in advance, as the block B, is occupied by another train, the train control apparatus H on the following train would be set into operation, because the presence of the forward train would cause a dcenergization of the corresponding track relay l2 and an interruption of the connection between the corresponding trans'l'ormer N and the track rails of the block in the rear, so that the signaling; current would cease to he'supplied to the following train. It will be noted that regardless of whether or not block B is occupied, a certain alternating current at the frequency of the transmission line lis supplied to the track rails 1 and 2 from the transformer T but this alternating current being of a different frequency than the signaling current supplied from the transmission line 6 is incapable of operating the sensitive relay F which will respond to current of only one frequency.

The reactance X and the condenser C are so proportioned relative to each other and rela tive to the reactance and resistance of the other parts of the circuit, particularly the coil K and the electromagrnet E, in accord ance with the well known principles of resonant circuits, so that for a given frequency, corresponding to the frequency of the signaling current supplied by the transmission line 6, the opposition to the flow of current througzl i the coil K and the electromagnet E is a minimum; whereas when currents of a different frequency flow in the tra :lr rails, the currents induced thereby in the coil K find such an increased opposition to the flow as to he almost entirely choked out. in other words, the circuit incl ding the coil K and the electromagnet E is tuned by the reactance X and the condenser C for resonance at a vcn frequency. The use of the reactance X and the condenser C for this purpose const utes one of the very important features oi this invention One advantage of so tuning'the car c cuit is that current in the traclr rail: of the frequency supplied from the transmission line i does not induce appreciable current in the cancircuit. A further advantage is that less current flowing in the track rails will cause a greater induced current in the car circuit, providing the frequency corresponds to the frequency for which the car circuit is tuned, due to the decrease in the total impedance of the car circuit. A still further advantage of this arrangement, which is of great importance with electrically propelled roads, is that a rapid rise or fall in the propulsion current flowing in the tract; rails, due to the starting or stopping of trains along the track, does not pro duce large or dangerous surges in the car circuit and in the relay circuit on the train. This is due to the fact that all current except of a predetermined frequency is choked out of the car circuit, so that variations in the amount of current flowing in the regardless of how great these variations may be, fail to produce corresponding variations in the car circuit and relay circuit on the train, unless the current in the track rails increases or decreases at a rate corresponding to the frequency for which the car circuit is tuned. in the case of electrically propelled cars, the rate of increase or decrease of the propulsion current in the track rails, caused by the starting or stopping of the cars, depends on the electrical characteristics of the circuit through which the propulsion current flows and in practice does not correspond with the rate of change of the alternating current used for signaling purposes.

2 shows the invention applied to a railway in which the trains are propelled by steam locomotives; and in view of the description and explanation hereinbefore given, and since the parts shown in Fig. 2 correspond with like parts shown in Fig. 1, a description in detail of the construction and op ration of the parts shown in Fig. 2 is unnecessary.

In Fig. 2 the condenser C included in the circuit of the coil K and the electromagnet E is so proportioned in capacity with i rence to the reactance ofthe circuit, especially the reactance of the electromagnet E and the coil K, that for the given frequency of the signaling current supplied by the trans mission line 6, a minimum opposition to the flow of current through this circuit exists. other words, the ca acity of the condenser C is selected with a view of tuning the circuit including the coil ii a d the electromagnet E for the frequency he signaling); cur rent, so that this circuZt is made to a large extent selective to signa ng); current and is also made more sensit. to the action of the signaling current'due to the resonant action of this circuit.

In certain types of amplifying devices, including the particular type illustrated in the draw n the an'iplilied current is a rectified urrent, that is, uni-directional, although periodically varying in intensity. In making bl ack rails,

9 p u 1 said transroriner being included in a norcuits will be apparent to those there is illustrated a modified arrangement of circuits for enabling alternating current to be supplied to the sensitive relay. In this modification, a transformer Z is introduced between the amplifying device and the relay, he primary of said transformer being includcd in a nornniiy cloud circuitwhich includes the local source of current and the amplifying device, and the secondary of mally closed circuit passing through the coils of the sen: tive relay F. -The action and operation of this modified a gement of cirsltillcd in the art.

This invention is applicable to train control systems oi various type :1 which it is necessary to have communication between a moving train and the track, and it may be used i of the factors determining the operation of the 'rain control apparatus, as Well as systems in which the train is controlled upon operation of its automatic train control, apparatus irrespective of speed or location with reference to other trains. I wish also to have it understood that my invention is not limited to the use of the particular type of amplifier or sensitive relay shown and described, and that my invention is applicable to systems in which'signaling current is taken inductively in other ways than by means of a coil from the track rails or other conductors along the track. 4 Althougl'i I have particularly described the construction of one physical embodiment of my invention, and explained the operation and principle thereof; nevertheless, Idesire to h "t understood that the form selected .ustrativc, but does not exhaust the embodimentsof the idea nderlying my invention. 7 claim as new and desireto secure sy l Patent of the United States, is: 1. In an automatic train control or cab signaling system, in combination: a railway vehicle; a stationary conductor extending along the path of movement of the vehicle; traffic controlled means for supplying a periodic signaling current to said conductor; a coil on the vehicle directly coupled in inductive relation with said conductor; a circuit on the vehicle including said coil and tuned sharply to resonance for the single particular frequency of said signaling current; an electrical amplifying device included directlyin said circuit; a relay affected only by current of the frequency of said signaling. current and controlled by the current supplied from said amplifying device; and train control apparatus on the vehicle controlled by said relay.

2. In a signaling system for electric railroads, in combination with a. railroad track segregated into blocks provided with track circuits and having thetrach rails carrying propulsion current and alternating current for the track circuits, of means controlled by each track circuit for normally supplying a periodic signaling current to the track rails of the block nextin the rear, a normally closed circuit on a vehicle resonant at the frequency of said signaling current and having a portion thereofdisposed in inductive relation to the track rails, a second normally closed circuit on the vehicle including a source of current and a relay, said relay being responsive only to periodic fluctuating current of the same frequency as said signaling current, train control means governed by saidrelay, and an amplifier on the vehicle governed by the first circuit for causing fluctuations of current of greater amplitude in the secondcircuit. r f i 3. In an automatic train control or cab signal system for railroads, which have the tracks divided into blocks each provided with a normally closed track circuit and a track relay, a source of alternatingcurrent along the tra'ckway, means controlled by the track relay of each block for supplying alternating current from said sourceto the track rails of the block next in the rear, a coil carried on a vehicle in front of the first pair of wheels and axle thereof and disposed over a track rail in inductive relation thereto, a condenser directly in series with said coil and turning it sharps ly to resonance for the particular frequency of said alternating current, an amplifyingdevice on the vehicle having its input connected to saidcoil, and a relay on the vehicle connected to the output circuit of said amplifyinherently responsive to operate its contacts only if energized with alternating current of said particular frequency.

4. In a train control system for governing train movement over track circuited blocks, each block having a track relay, a source of alternating current of a predetermined fre quency along the trackway, means controlled by the track relay of each block for connect ing said sourceacross the track rails, of the next block in the rear at the-exit end thereof, whereby alternating current from said source at, any instant may flow through the track rails in opposite directions in front of a train in the block, a coil carrledon a train in front of the first wheels and a-Xlethereof, automatlc train control apparatus on the vehicle adapted to assume its active condition whenever deenergized, a relay on the vehicle maintaining said apparatus energized and inactive only so long as alternating current of said predetermined frequency is supplied to said relay, an

amplifying device on the vehicle having its output circuit connected to said relay and its input circuit connected to said coil, and means for tuning said coil sharply to resonance for the single particular frequency of said source.

5. In an automatic train control or cab signal system for railroads, the combination With a railroad track divided into insulated track sections, a track relay for each section, a trackway source of alternating current, means controlled by the track relay of each track section for supplying an alternating difference of potential from said source across the track rails at the exit end of a track section in the rear, a coil carried on a vehicle in front of the first pair of Wheels and axles thereof and disposed in inductive relation to one of the track rails, a circuit on the vehicle including said coil and tuned sharply to resonance for the particular frequency of the alternating current from said source, and safety means on the vehicle maintained inactive only so long as supplied With energy from said circuit, said safety means being connected to said circuit and comprising an electro-responsive device of the polarized tuned reed type and an amplifier device of the microphonic type.

CHARLES F. ESTWICK. 

